Improvements in positioning systems are making autonomous machines, such as autonomous earthmoving machines, a reality.
In order to achieve autonomy, a machine must at all times be able to determine its position relative to its environment. One system commonly used to achieve this goal is the Global Positioning System or GPS. The GPS consists of a plurality of satellites which transmit electromagnetic signals. A GPS receiver located within the range of the satellites receives signals from the satellites and determines the position of the receiver using triangulation methods.
It is possible to use a GPS receiver alone for positioning. However, when high accuracy is required, integrated positioning systems are preferred. An integrated positioning system uses measurements from several different types of sensors to achieve highly accurate positioning information.
Many examples of integrated positioning systems are known. Such integrated systems use GPS navigation signals as well as measurements from inertial and other machine motion type sensors to produce more accurate position estimates. However, these systems are generally of custom design and are therefore expensive and burdensome to implement.
Integrated systems are limited by reliance on the machine motion type sensors. Their accuracy is limited, thus, they are typically used only for short distances.
Typically, in most integrated systems it is assumed that a position estimate from a GPS receiver is accurate. However, experience has shown that GPS position estimates also tend to drift. Over-reliance on GPS position estimates decreases the usability of the overall autonomous system.
The present invention is directed at one or more of the problems as set forth above.